The present techniques relate generally to bit-wise holographic data storage techniques. More specifically, the techniques relate to methods and systems for parallel replication in optical disks.
As computing power has advanced, computing technology has entered new application areas, such as consumer video, data archiving, document storage, imaging, and movie production, among others. These applications have provided a continuing push to develop data storage techniques that have increased storage capacity and increased data rates.
One example of the developments in data storage technologies may be the progressively higher storage capacities for optical storage systems. For example, the compact disc, developed in the early 1980s, has a capacity of around 650-700 MB of data, or around 74-80 minutes of a two channel audio program. In comparison, the digital versatile disc (DVD) format, developed in the early 1990s, has a capacity of around 4.7 GB (single layer) or 8.5 GB (dual layer). Furthermore, even higher capacity storage techniques have been developed to meet increasing demands, such as the demand for higher resolution video formats. For example, high-capacity recording formats such as the Blu-ray Disc™ format is capable of holding about 25 GB in a single-layer disk, or 50 GB in a dual-layer disk. As computing technologies continue to develop, storage media with even higher capacities may be desired. Holographic storage systems and micro-holographic storage systems are examples of other developing storage technologies that may achieve increased capacity requirements in the storage industry.
Holographic storage is the storage of data in the form of holograms, which are images of three dimensional interference patterns created by the intersection of two beams of light in a photosensitive storage medium. Both page-based holographic techniques and bit-wise holographic techniques have been pursued. In page-based holographic data storage, a signal beam containing digitally encoded data (e.g., a plurality of bits) is superposed on a reference beam within the volume of the storage medium resulting in a chemical reaction which modulates the refractive index of the medium within the volume. Each bit is therefore generally stored as a part of the interference pattern. In bit-wise holography or micro-holographic data storage, every bit is written as a micro-hologram, or Bragg reflection grating, typically generated by two counter-propagating focused recording beams. The data are then retrieved by using a read beam to reflect off the micro-hologram to reconstruct the recording beam.
Holographic storage systems provide much higher storage capacities than prior optical systems. However, due in part to the small physical size of micro-holograms and the closely spaced tracks and/or layers in a storage medium (e.g., an optical disk), the two counter-propagating beams are dynamically overlapped for accurate and efficient micro-hologram recording. Simpler or more efficient techniques for recoding an optical disk with micro-holograms may be advantageous.